A Few Fixes

Just saw your talk from 2012 re: activewarehouse-etl and thought I'd fire up your examples.  I hit a few small snags and fixed them:

- Migrated from .rvmrc to .ruby-version
- Updated the source entry in the Gemfile to avoid a warning from Bundler
- My git --shortstat seems to be producing different output from what etl/extract.ctl was expecting, so I threw in a few quick regexps to handle the variations.  Not elegant, but they work.

Thanks for the great sample code.  It's helping me get off the ground pretty quickly.